Saurobacciosides A - C: three new glycosides from Sauropus bacciformis with their cytotoxic activity

Article abstract of DOI:10.1080/14786419.2021.1892670

Three new glycosides, named as saurobaccioside A (1), saurobaccioside B (2), saurobaccioside C (3), together with five known magastigmanes, canangaionoside (4), (6S,9S)-roseoside (5), cucumegastigmane I (6), icariside B5 (7), linarionoside A (8) were isolated from the whole plant of Sauropus bacciformis (L.) Airy Shaw. Their structures were established by extensive spectroscopic analysis (UV, IR, HR-ESI-MS and NMR) and by comparison of the spectral data with those reported in the literature. The absolute configurations of compounds 2 and 3 were elucidated by experimental CD spectra. Compounds 1-8 were screened their cytotoxic activities towards CAL27 and MDAMB231 cancer cell lines. Compound 1 exhibited significant cytotoxic activity towards CAL27 and MDAMB231 cell lines with IC₅₀ values of 3.21 ± 0.23 and 4.75 ± 0.17 μM, respectively, which were smaller than those of positive control capecitabine (IC₅₀: 8.20 ± 0.75 and 5.20 ± 0.89 μM). Other compounds (2-8) were inactive.

Full text of DOI:10.1080/14786419.2021.1892670

Natural Product Research
Formerly Natural Product Letters
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/gnpl20
Saurobacciosides A - C: three new glycosides from
Sauropus bacciformis with their cytotoxic activity
Phan Thi Thanh Huong, Bui Huu Tai, Nguyen Xuan Nhiem, Nguyen Xuan
Cuong, Tran Hong Quang, Vu Kim Thu, Pham Hai Yen & Phan Van Kiem
To cite this article: Phan Thi Thanh Huong, Bui Huu Tai, Nguyen Xuan Nhiem, Nguyen Xuan
Cuong, Tran Hong Quang, Vu Kim Thu, Pham Hai Yen & Phan Van Kiem (2021): Saurobacciosides
A - C: three new glycosides from Sauropusꢀbacciformis with their cytotoxic activity, Natural Product
Research, DOI: 10.1080/14786419.2021.1892670
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NATURAL PRODUCT RESEARCH
https://doi.org/10.1080/14786419.2021.1892670
Saurobacciosides A - C: three new glycosides from
Sauropus bacciformis with their cytotoxic activity
Phan Thi Thanh Huonga, Bui Huu Taia,b, Nguyen Xuan Nhiema,b, Nguyen Xuan
Cuonga, Tran Hong Quanga, Vu Kim Thuc, Pham Hai Yena and Phan Van Kiema,b
aInstitute of Marine Biochemistry, Vietnam Academy of Science and Technology (VAST), Hanoi,
b
Vietnam; Graduate University of Science and Technology, Vietnam Academy of Science and
c
Technology, Hanoi, Vietnam; Hanoi University of Mining and Geology, Hanoi, Vietnam
ABSTRACT
ARTICLE HISTORY
Received 19 December 2020
Accepted 15 February 2021
Three new glycosides, named as saurobaccioside A (1), saurobac-
cioside B (2), saurobaccioside C (3), together with five known
magastigmanes, canangaionoside (4), (6S,9S)-roseoside (5), cucu-
megastigmane I (6), icariside B5 (7), linarionoside A (8) were iso-
lated from the whole plant of Sauropus bacciformis (L.) Airy Shaw.
Their structures were established by extensive spectroscopic ana-
lysis (UV, IR, HR-ESI-MS and NMR) and by comparison of the spec-
tral data with those reported in the literature. The absolute
configurations of compounds 2 and 3 were elucidated by experi-
mental CD spectra. Compounds 1-8 were screened their cytotoxic
activities towards CAL27 and MDAMB231 cancer cell lines.
Compound 1 exhibited significant cytotoxic activity towards
CAL27 and MDAMB231 cell lines with IC50 values of 3.21 0.23
and 4.75 0.17 mM, respectively, which were smaller than those of
positive control capecitabine (IC50: 8.20 0.75 and 5.20 0.89 mM).
Other compounds (2-8) were inactive.
KEYWORDS
Sauropus bacciformis;
Phyllanthaceae; saurobac-
ciosides; glycosides;
norsesquiterpenoids
1. Introduction
The genus Sauropus (family Phyllanthaceae) comprises about 40 species of herbs,
shrubs or subshrubs, sometimes with woody bases. They are distributed in Southeast
Asia (Thailand up to Vietnam), Malesia and Australia (Peter 2003). Some Sauropus
CONTACT Phan Van Kiem
phankiem@yahoo.com
Supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2021.1892670.
ß 2021 Informa UK Limited, trading as Taylor & Francis Group

2
P. T. T. HUONG ET AL.
species are highly valued due to their high nutritive value and inexpensive source of
dietary protein which is also used in traditional medicine (Faisal and Muhammad 2020;
Tamanna and Raviraja 2020). The phytochemical investigation of Sauropus genus sug-
gested the presence of carotenoids, flavonoids, lignans, megastigmanes (Tripetch et al.
2003; Faisal and Muhammad 2020; Tamanna and Raviraja 2020). The methanol extract
of whole plant of Sauropus bacciformis has potent hepatoprotective action upon car-
bon tetrachloride induced hepatic damage in rats (Sheela and Udhayakumari 2018). In
Vietnam, S. bacciformis plant is widely distributed and used in folk medicine for treat-
ment of snakebite, detoxify, diarrhea, hepatitis (Ho 1999; Chi 2012). However, up to
now, there has been no publication of the chemical composition of S. bacciformis. This
paper reports three new glycosides (1–3) together with five known magastigmanes
from the whole plant of Sauropus bacciformis. Their cytotoxic activity towards human
oral cancer cell lines (CAL27) and human breast cancer cell lines (MDAMB231) were
also evaluated.
2. Results and discussion
Compound 1 was obtained as colorless amorphous powder. Its molecular formula was
determined to be C40H48O21 by quasi-molecular ion peaks in HR-ESI-MS (m/z 899.2390
[M þ 35Cl]-, calcd. for C40H48O2135Cl: 899.2377; m/z 901.2393 [M þ 37Cl]-, calcd. for
C40H48O2137Cl: 901.2347) and in conjunction with 13C NMR data, indicating 17 degrees
1
of unsaturation. The H NMR spectrum of 1 observed resonant signals corresponding
to a phenyl group [dH 8.09 (2H, dd, J ¼ 8.0, 1.5 Hz, H-20, H-60), 7.49 (2H, dd, J ¼ 8.0, 8.0,
Hz, H-30, H-50), 7.61 (1H, tt, J ¼ 8.0, 1.5 Hz, H-40)], a para-substituted phenyl group [dH
8.10 (2H, br d, J ¼ 8.5 Hz, H-20000, H-60000), 6.98 (2H, br d, J ¼ 8.5 Hz, H-30000, H-50000)], two
anomeric protons [dH 5.65 and 4.38 (each 1H, d, J ¼ 8.0 Hz)], and a methyl group [dH
0.91 (3H, d, J ¼ 7.0 Hz)]. The 13C NMR spectrum of 1 showed signals of 40 carbons
which were assigned by HSQC spectrum into nine non-protonated carbons, 24
methine carbons, six methylene carbons, and one methyl carbon. In particularly, eight
signals of twelve aromatic carbons together with HMBC correlations from H-20/H-60 (dH
8.09) to C-70 (dC 168.1), from H-20000/H-60000 (dH 8.10) to C-70000 (dC 167.9)/C-40000 (dC 163.1)
indicated the presence of a benzoyl and a para-hydroxy benzoyl groups. Two anome-
ric carbons (dC 93.7 and 106.1) and 10 oxygenated carbons suggested for two hexose
moieties. The chemical shift value of C-200 resonanced at dC 83.3 suggested that a
glycoside linkage was formed through C-200. Remaining 14 carbons expected for a nor-
sesquiterpene backbone of the aglycone. Structure of aglycone moiety was further
elucidated by COSY and HMBC analysis as shown in Figure S1. COSY cross peaks of H-
1 (dH 3.96)/H-2(dH 2.07 and 1.81)/H-3 (dH 2.94)/H-4 (dH 2.40 and 1.90)/H-5 (dH 4.31), as
well as HMBC correlations from H-1 and H-5 to C-6 (dC 75.5) established structure of
cyclohexane ring (A-ring). On the other hand, COSY cross peaks of H2-9 (dH 2.29 and
1.99)/H-10 (dH 5.33)/H-11 (dH 2.18)/H2-12 (dH 4.06 and 3.58), and of H-11 (dH 2.18)/H3-
14 (dH 0.91), together with HMBC correlations from H2-9 and H2-12 to C-8 (dC 100.6)
revealed structure of tetrahydropyrane ring (B-ring). Deshielded carbon signals of C-7
(dC 213.7) and HMBC correlation from H-5 (dH 4.31) to C-8 (dC 100.6) suggested the
formation of ketone functional group at C-7 and an ether-bridge between C-5 and C-

NATURAL PRODUCT RESEARCH
3
Figure 1. Chemical structures of compounds 1–8.
8. HMBC correlations from H-3 (dH 2.94) to C-13 (dC 175.9), from H-10 (dH 5.33) to C-70
(dC 168.1) confirmed the presence of carboxyl group at C-13 and O-benzoyl group at
C-10, respectively. Thus, aglycone moiety of compound 1 was then identified to be
phyllaemblic acid as previous described (Zhang et al. 2000). Moreover, 1H and 13C
NMR spectral data of 1 were recognized close similarity to those of phyllaemblicin B,
except for the observations of additional signals corresponding to para-hydroxy
benzoyl group. The COSY cross peaks between H-1000 (dH 4.38) and H-2000 (dH 3.44),
between H-2000 and H-3000 (dH 5.13) together with HMBC correlation from H-3000 to
C-70000 (dC 167.9) were observed confirming that the para-hydroxy benzoyl group was
linked to C-3000 of glcII. Continuously, COSY cross peaks from H-100 (dH 5.65) to H-200 (dH
3.56) together with HMBC correlation from H-1000 (dH 4.38) to C-200 (dC 83.3) confirmed
the glcII linked to C-200 of the glcI. The sugar linkages must be in the b-form as judged
from the coupling constants (J ¼ 8.0 Hz) of the anomeric protons at dH 5.65 and 4.38.
Except for the additional para-hydroxy benzoyl group, the proton and carbon chemical
1
shifts as well as the H-1H coupling constants of compound 1 matched perfectly with
the corresponding data of phyllaemblicin B (1a) (Table S3) suggesting that the relative
configuration of 1 was similar to that of phyllaemblicin B (Zhang et al. 2000), which
was further confirmed by NOESY spectrum. Detailed key NOESY correlations in the
aglycone moiety of 1 were shown in Figure S1a. Finally, the presence of D-glucose in
the acid hydrolysis product of compound 1 was confirmed by HPLC analysis.
Consequently, the chemical structure of compound 1 was established as shown
in Figure 1, a new compound named as saurobaccioside A.
Compound 2 was obtained as colorless amorphous powder. Its molecular formula
was determined to be C28H36O10 by quasi-molecular ion peaks in HR-ESI-MS (m/z
567.2006 [M þ 35Cl]- (Calcd. for [C28H36O1035Cl]-, 567.1997), m/z 569.1994 [M þ 37Cl]-
1
(Calcd. for [C28H36O1037Cl]-, 569.1967), indicating 11 degrees of unsaturation. The H
NMR spectrum of 2 exhibited three methyl singlet signals at dH 0.99, 1.04, 1.96

4
P. T. T. HUONG ET AL.
(each, 3H) and one methyl doublet at dH 1.30 (J ¼ 6.5 Hz), four olefinic protons of two
trans double bonds at dH 5.75/5.90 (J ¼ 16.0 Hz) and dH 6.34/7.66 (J ¼ 16.0 Hz), a broad
singlet of olefinic proton at dH 5.90, a para-substituted benzene ring at dH 7.47 and
6.83 (each, 2H, br d, J ¼ 8.5 Hz), and one anomeric proton at dH 4.31 (d, J ¼ 8.0 Hz). The
13C NMR spectrum of 2 showed signals of 28 carbons which were assigned by HSQC
spectrum into seven quaternary carbons, 15 methine carbons, two methylene carbons,
and four methyl carbon. One ketone carbon and one carboxylate group were identi-
fied at dC 201.1 and 169.0, respectively. One coumaroyl moiety was identified by sig-
nals of the para-substituted benzene ring at dC 127.2 (C), 116.9 (CH x 2), 131.2 (CH x
2), 161.4 (C), a trans double bond at dC 114.9 and 146.9, and of one carboxylate group
at dC 169.0, which were further confirmed by HMBC correlation from H-700 (dH 7.66) to
C-900 (dC 169.0) and C-200 (dC 131.2). In addition, a set of signals of dC 101.3, 74.9, 78.2,
71.9, 75.6 (5 CH), and 64.7 (CH2) was consistent with a glucose having an ester linkage
at C-60. Remaining 13 carbon signals including four methyl groups (dC 19.6, 22.2, 23.5,
24.7), two double bond (127.1/166.9, 133.9/133.6), one C ¼ O carbon (dC 201.1), two
carbons bearing oxygene atoms at dC 79.9 and 74.8, were assigned for the megastig-
mane having ketone group at C-3, two double bonds at C-4/C-5 and C-7/C-8, and one
hydroxyl group at C-6 and an ether linkage at C-9 as roseosides (Son et al. 2015). The
NMR data of 2 were found to be similar to the corresponding data of 60-O-caffeoyl-
(6S,9R)-roseoside (Son et al. 2015) except for the data of the caffeoyl group were
replaced by the data of coumaroyl group of 2. This evidence was further confirmed by
COSY and HMBC correlations as shown in Figure S1. In the literature, the 13C NMR
chemical shifts of the (9 R)- and (9S)-configuration are 77.0 and 74.7, respectively
(Yamano and Ito 2005). So that, the 13C NMR chemical shifts of C-9, dC 74.8, suggested
(9S)-configuration of 2. Comparison to literature data (Yamano and Ito 2005), the
stereochemistry at C-6 was established as 6S on the basis of circular dichroism (CD)
with the exhibition of a positive maximum at 240 nm (De þ 19.5). Furthermore, the
1
coupling constant (J ¼ 8.0 Hz) observed for the anomeric proton in the H NMR spec-
trum of 2 indicated the b-glucoside linkage for the O-glucose moiety. Finally, the pres-
ence of D-glucose in the acid hydrolysis product of compound 2 was confirmed by
HPLC analysis. Consequently, the chemical structure of compound 2 was established
as shown in Figure 1, a new compound named as saurobaccioside B.
Compound 3 was obtained as colorless amorphous powder. Its molecular formula
was determined to be C28H36O10 by quasi-molecular ion peaks in HR-ESI-MS (m/z
567.2004 [M þ 35Cl]- (Calcd. for [C28H36O1035Cl]-, 567.1997), m/z 569.1995 [M þ 37Cl]-
(Calcd. for [C28H36O1037Cl]-, 569.1967), indicating 11 degrees of unsaturation. The NMR
spectra of 3 were similar to those of 2 except for slight differences at the coumaroyl
group (Table S4). The smaller proton coupling constant (J ¼ 13.0 Hz) of H-700 (dH 6.85)
and H-800 (dH 5.77) indicated cis-configuration of the double bond at C-700/C-800. The
NMR assignments of 3 were assigned by comparing its NMR data with the correspond-
ing data of 2 and further confirmed by HSQC, HMBC, COSY, and NOESY spectra. The
13C NMR chemical shifts of C-9, dC 74.7, suggested (9S)-configuration of 3 (Yamano
and Ito 2005). The CD spectrum of 3 exhibited a positive maximum at 240 nm
(De þ 21.0) indicated the stereochemistry at C-6 as 6S (Yamano and Ito 2005; Son et al.
2015). The proton coupling constant of the anomeric proton at dH 4.28 (J ¼ 8.0 Hz)

NATURAL PRODUCT RESEARCH
5
confirmed the b-form of the glucoside linkage. The presence of D-glucose was indi-
cated by acid hydrolysis product of 3. Consequently, the chemical structure of com-
pound 3 was established as shown in Figure 1, a new compound named as
saurobaccioside C.
The other compounds isolated from Sauropus bacciformis were identified as canan-
gaionoside (4) (Katsuyoshi et al. 2010), (6S,9S)-roseoside (5) (Yamano and Ito 2005),
cucumegastigmane I (6) (Hisahiro et al. 2007), icariside B5 (7) (Katsuyoshi et al. 2010b),
linarionoside A (8) (Otsuka 1994) by comparisons of their NMR data with those data
reported in the literature and found to match.
Cytotoxic activity of compounds 1-8 were assessed towards CAL27 and MDAMB231
human cancer cell lines. Firstly, each compound was screened cytotoxic effects at con-
centration of 30 mM. As shown in the Table S1, compound 1 significantly exhibited
cytotoxic effects by showing low percentages of cell viability in both tested cell lines
(14.0 0.01% and 25.6 0.72% for CAL27 and MDAMB231 experiments, respectively).
The cell viability percentages were in range from 71.3 0.74% to 95.4 0.62 in the
presence of compounds 2-8 suggested that those compounds were inactive.
Compound 1 was then performed dose-dependent study. Its IC50 values were calcu-
lated to be 3.21 0.23 mM and 4.75 0.17 mM against CAL27 and MDAMB231 cells,
respectively (Table S2). Phyllaemblic acid and its derivatives such as phyllaemplicins
were previously reported to be major components of Phyllanthus emblica (Zhang et al.
2004; Lv et al. 2015). These compounds exhibited potent antiviral and cytotoxic activ-
ities. Interesting that, phyllaemblic acid and its monoglucoside derivative (phyllaemblic
acid b-D-glucopyranosyl ester) did not show cytotoxic activity but several phyllaemblic
acid glycosides containing two or more monosaccharide units significantly exhibited
cytotoxic activity (Zhang et al. 2004). In our study, compound 1 was a diglucoside
derivative of phyllaemblic acid and showed significantly cytotoxic effect against CAL27
and NDAMB231 cells.
3. Experimental
3.1. General
Optical rotation was measured on a Jasco P2000 polarimeter. IR spectrum was
recorded on a Spectrum Two FT-IR spectrometer. CD spectrum was obtained on a
Chirascan spectrometer (Applied Photophysics, Surrey, UK). HR-ESI-MS was acquired on
an Agilent 6530 Accurate Mass Q-TOF LC/MS. NMR spectra were recorded on a Bruker
500 MHz spectrometer. Preparative HPLC were run on an Agilent 1100 system includ-
ing quaternary pump, autosampler, DAD detector, and preparative HPLC column YMC
J’sphere ODS-H80 (4 mm, 20 ꢀ 250 mm). Isocratic mobile phase with the flow rate of
3 mL/min was used in pre-HPLC. The compound was monitored at wavelengths of
205, 230, 254, and 280 nm. Flash column chromatography was performed using silica
gel, reversed phase C-18, and diaion HP-20 resins as stationary phase. Thin layer chro-
matography was carried out on pre-coated silica gel 60 F254 and RP-18 F254S plates.
The spots were detected by spraying with aqueous solution of H2SO4 5% followed by
heating with a heat gun.

6
P. T. T. HUONG ET AL.
3.2. Plant material
The aerial parts of Sauropus bacciformis (L.) Airy Shaw were collected at Xuan Thuy
District, Nam Dinh Province, Vietnam in Jun 2019 and taxonomically identified by Dr
Nguyen The Cuong at the Institute of Ecology and Biological Resources, VAST.
Voucher specimen (NCCT-P118) was deposited at the Institute of Marine
Biochemistry, VAST.
3.3. Extraction and isolation
The dried powder of aerial parts of Sauropus bacciformis (10 kg) were sonicated with
methanol (3 times, each 15 L MeOH). After removal of solvent, the MeOH extract
(350 g) was suspended with water and then partitioned with dichloromethane and
then ethyl acetate to give corresponding residues, (HSBD, 90 g) and (HSBE, 8 g), and
water layer (HSBW). The HSBE (8 g) was chromatographed on a RP-18 column eluting
with MeOH/water (1.2/1, v/v) to give seven fractions, HSBE1 ! HSBE7. HSBE4 (160 mg)
was chromatographed on HPLC (J’sphere H-80 column, 250 mm length x 20 mm ID,
eluting with 30% acetonitrile in water, a flow rate of 2.5 mL/min) to give compounds 1
(4.5 mg) and 6 (6.0 mg). HSBE5 (259 mg) was chromatographed on HPLC (J’sphere H-
80 column, 250 mm length x 20 mm ID, eluting with 30% acetonitrile in water, a flow
rate of 2.5 mL/min) to give compounds 2 (4.0 mg) and 3 (5 mg). The water layer
(HSBW) was chromatographed on a Diaion HP-20 column, first eluting with water to
remove sugar components, then increasing concentration of MeOH in water (25, 50,
75, and 100%) to obtain four fractions, HSBW1 (6.8 g), HSBW2 (17 g), HSBW3 (8.5 g),
HSBW4 (2.9 g). The HSBW2 fraction was subjected on a silica gel CC eluting with gradi-
ent solvent of CH2Cl2/MeOH (30/1, 10/1, 5/1, 0/1 v/v) to give four fractions, HSBW2A
! HSBW2D. The HSBW2B (685 mg) was re-chromatographed on a silica gel CC eluting
with CH2Cl2/MeOH (10/1, v/v) to give five smaller sub-fractions, HSBW2B1 !
HSBW2B5. HSBW2B1 (56 mg) was chromatographed on HPLC (J’sphere H-80 column,
250 mm length x 20 mm ID, eluting with 20% acetonitrile in water, a flow rate of
2.5 mL/min) to give 5 (5.0 mg). HSBW2B3 (46 mg) was chromatographed on HPLC
(J’sphere H-80 column, 250 mm length x 20 mm ID, eluting with 20% acetonitrile in
water, a flow rate of 2.5 mL/min) to give compounds 7 (8.0 mg) and 8 (11.0 mg).
HSBW2C (3 g) was chromatographed on a sephadex LH-20 column, eluting with
MeOH/water (1/1, v/v) to give two fractions, HSBW2C1 and HSBW2C2. HSBW2C1
(352 mg) was chromatographed on a RP-18 column eluting with MeOH/water (1/1.5, v/
v) to give four smaller sub-fractions, HSBW2C1A ! HSBW2C1D. HSBW2C1B (35 mg)
was chromatographed on HPLC (J’sphere H-80 column, 250 mm length x 20 mm ID,
eluting with 16% acetonitrile in water, a flow rate of 2 mL/min) to give 4 (4.7 mg).
3.3.1. Saurobaccioside A (1)
25
Colorless amorphous powder, ½aꢁD : þ5.5ꢂ (c 0.1, MeOH); UV (MeOH) kmax 234,
257 nm; IR (KBr): ꢀmax 3360 (broad), 2932, 1707, 1607, 1278, 1075 cmꢃ1; HR-ESI-MS m/z
899.2390 [M þ 35Cl]-, calcd. for C40H48O2135Cl: 899.2377; m/z 901.2393 [M þ 37Cl]-,
1
calcd. for C40H48O2137Cl: 901.2347. H-NMR (CD3OD, 500 MHz), d (ppm): 3.96 (1H, br s,
H-1), 2.07 (1H, br d, J ¼ 14.5 Hz, Heq-2), 1.81 (1H, ddd, J ¼ 3.0, 13.0, 14.5 Hz, Hax-2), 2.94

NATURAL PRODUCT RESEARCH
7
(1H, m, H-3), 2.40 (1H, br d J ¼ 14.5 Hz, Heq-4), 1.90 (1H, ddd, J ¼ 4.0, 13.0, 14.5 Hz, Hax-
4), 4.31 (1H, br s, H-5), 2.29 (1H, dd, J ¼ 3.0, 14.5 Hz, Ha-9), 1.99 (1H, dd, J ¼ 3.0, 14.5 Hz,
Hb-9), 5.33 (1H, br d, J ¼ 3.0 Hz, H-10), 2.18 (1H, m, H-11), 4.06 (1H, dd, J ¼ 11.0,
11.0 Hz, Hax-12), 3.58 (1H, dd, J ¼ 5.0, 11.0 Hz, Heq-12), 0.91 (1H, d, J ¼ 7.0 Hz, H-14),
Benzoyl: 8.09 (2H, dd, J ¼ 8.0, 1.5 Hz, H-20, H-60), 7.49 (2H, dd, J ¼ 8.0, 8.0 Hz, H-30, H-50),
7.61 (1H, tt, J ¼ 8.0, 1.5 Hz, H-40), GlcI: 5.65 (1H, d, J ¼ 8.0 Hz, H-100), 3.56 (1H, dd,
J ¼ 8.0, 9.0 Hz, H-200), 3.63 (1H, t, J ¼ 9.0 Hz, H-300), 3.57 (1H, t, J ¼ 9.0 Hz, H-400), 3.44 (1H,
m, H-500), 3.81 (1H, dd, J ¼ 5.5, 12.0 Hz, H-600), 3.95 (1H, dd, J ¼ 2.0, 12.0 Hz, H-600), GlcII:
4.38 (1H, d, J ¼ 8.0 Hz, H-1000), 3.44 (1H, dd, J ¼ 8.0, 9.0 Hz, H-2000), 5.13 (1H, t, J ¼ 9.0 Hz,
H-3000), 3.61 (1H, t, J ¼ 9.0 Hz, H-4000), 2.93 (1H, m, H-5000), 3.60-3.64 (2H, H-6000), p-
hydroxy-benzoyl: 8.10 (1H, br d, J ¼ 8.5 Hz, H-20000, H-60000), 6.98 (1H, br d, J ¼ 8.5 Hz, H-
3
0000, H-50000). 13C-NMR (CD3OD, 125 MHz), d (ppm): 71.5 (C-1), 32.2 (C-2), 32.2 (C-3), 29.4
(C-4), 76.3 (C-5), 75.5 (C-6), 213.7 (C-7), 100.6 (C-8), 32.8 (C-9), 70.4 (C-10), 34.4 (C-11),
63.5 (C-12), 175.9 (C-13), 13.1 (C-14), 131.7 (C-10), 130.7 (C-20, C-60), 129.4 (C-30, C-50),
134.1 (C-40), 168.1 (C-70), GlcI: 93.7 (C-100), 83.3 (C-200), 77.9 (C-300), 70.6 (C-400), 79.1 (C-
500), 62.4 (C-600), GlcII: 106.1 (C-1000),74.2 (C-2000), 79.5 (C-3000), 68.9 (C-4000), 77.6 (C-5000),
61.6 (C-6000), p-hydroxy-benzoyl: 123.2 (C-10000), 133.2 (C-20000, C-60000), 116.6 (C-30000, C-
5
0000), 163.2 (C-40000), 167.9 (C-70000).
3.3.2. Saurobaccioside B (2)
25
Colorless amorphous powder, ½aꢁD : þ 5.1ꢂ (c 0.1, MeOH); UV (MeOH) kmax 232,
314 nm; IR (KBr): ꢀmax 3415 (broad), 2971, 1695, 1649, 1604, 1168, 1040 cmꢃ1; CD
(MeOD) mdeg(k): þ19.5(240). HR-ESI-MS m/z 567.2006 [M þ 35Cl]- (Calcd. for
[C28H36O1035Cl]-, 567.1997), m/z 569.1994 [M þ 37Cl]- (Calcd. for [C28H36O1037Cl]-,
1
569.1967). H-NMR (CD3OD, 500 MHz), d (ppm): 2.17 (1H, d, J ¼ 17.0 Hz, Ha-2), 2.52 (d,
J ¼ 17.0 Hz, Hb-2), 5.90 (1H, brs, H-4), 5.90 (1H, d, J ¼ 16.0 Hz, H-7), 5.75 (1H, dd,
J ¼ 16.0, 7.0 Hz, H-8), 4.47 (1H, m, H-9), 1.30 (3H, d, J ¼ 6.5 Hz, H-10), 1.04 (3H, s, H-11),
0.99 (3H, s, H-12), 1.96 (3H, d, J ¼ 2.0 Hz, H-13), Glc: 4.31 (1H, d, J ¼ 8.0 Hz, H-10), 3.25
(1H, dd, J ¼ 8.0, 9.0 Hz, H-20), 3.33 (1H, t, J ¼ 9.0 Hz, H-30), 3.33 (1H, t, J ¼ 9.0 Hz, H-40),
3.41 (1H, m, H-50), 4.51 (1H, dd, J ¼ 2.0, 12.0 Hz, Ha-60), 4.32 (dd, 6.0, 12.0 Hz, Hb-60), (E)-
coumaroyl: 7.47 (2H, br d, J ¼ 8.5 Hz, H-200, H-600), 6.83 (2H, br d, J ¼ 8.5 Hz, H-300, H-500),
7.66 (1H, d, J ¼ 16.0 Hz, H-700), 6.34 (1H, d, J ¼ 16.0 Hz, H-800). 13C-NMR (CD3OD,
125 MHz), d (ppm): 42.4 (C-1), 50.8 (C-2), 201.1 (C-3), 127.1 (C-4), 166.9 (C-5), 79.9 (C-6),
133.9 (C-7), 133.6 (C-8), 74.8 (C-9), 22.2 (C-10), 23.5 (C-11), 24.7 (C-12), 19.6 (C-13), Glc:
101.3 (C-10), 74.9 (C-20), 78.2 (C-30), 71.9 (C-40), 75.6 (C-50), 64.7 (C-60), (E)-coumaroyl:
127.2 (C-100), 131.2 (C-200, C-600), 116.9 (C-300, C-500), 161.4 (C-400), 146.9 (C-700), 114.9 (C-
800), 169.0 (C-900).
3.3.3. Saurobaccioside C (3)
25
½aꢁD : þ 4.2ꢂ (c 0.1, MeOH); UV (MeOH) kmax 232, 314 nm; IR (KBr): ꢀmax 3382 (broad),
2970, 1696, 1604, 1651, 1169, 1054 cmꢃ1; CD (MeOD) mdeg(k): þ21.0(240). HR-ESI-MS
m/z 567.2004 [M þ 35Cl]- (Calcd. for [C28H36O1035Cl]-, 567.1997), m/z 569.1995 [M þ
37Cl]- (Calcd. for [C28H36O1037Cl]-, 569.1967).
1H-NMR (CD3OD, 500 MHz), d (ppm): 2.19 (1H, d, J ¼ 17.0 Hz, Ha-2), 2.56 (1H, d,
J ¼ 17.0 Hz, Hb-2), 5.87 (1H, brs, H-4), 5.86 (1H, d, J ¼ 16.0 Hz, H-7), 5.72 (1H, dd,

8
P. T. T. HUONG ET AL.
J ¼ 16.0, 7.0 Hz, H-8), 4.39 (1H, m, H-9), 1.26 (3H, d, J ¼ 6.5 Hz, H-10), 1.05 (3H, s, H-11),
1.00 (3H, s, H-12), 1.95 (3H, s, H-13), Glc: 4.28 (1H, d, J ¼ 8.0 Hz, H-10), 3.23 (1H, dd,
J ¼ 8.0, 9.0 Hz, H-20), 3.31 (1H, t, J ¼ 9.0 Hz, H-30), 3.30 (1H, t, J ¼ 9.0 Hz, H-40), 3.35 (1H,
m, H-50), 4.45 (1H, dd, J ¼ 2.0, 12.0 Ha-60), 4.29 (1H, dd, J ¼ 6.0, 12.0 Hb-60), (Z)-cou-
maroyl: 7.67 (2H, br d, J ¼ 8.5 Hz, H-200, H-600), 6.78 (2H, br d, J ¼ 8.5 Hz, H-300, H-500),
6.85 (1H, d, J ¼ 13.0 Hz, H-700), 5.77 (1H, d, J ¼ 13.0 Hz, H-800). 13C-NMR (CD3OD,
125 MHz), d (ppm): 42.4 (C-1), 50.8 (C-2), 201.2 (C-3), 127.1 (C-4), 167.0 (C-5), 79.9 (C-6),
134.0 (C-7), 133.6 (C-8), 74.7 (C-9), 22.3 (C-10), 23.5 (C-11), 24.7 (C-12), 19.6 (C-13), Glc:
101.1 (C-10), 74.9 (C-20), 78.3 (C-30), 71.8 (C-40), 75.6 (C-50), 64.5 (C-60), (Z)-coumaroyl:
00
127.5 (C-100), 133.8 (C-200, C-6 ), 116.0 (C-300, C-500), 160.2 (C-400), 145.0 (C-700), 116.2 (C-
800), 168.1 (C-900).
4. Conclusions
Three new glycosides named as saurobacciosides A-C (1-3) were identified from the
whole plant of Sauropus bacciformis (L.) Airy Shaw. Their structures were established
by extensive spectroscopic analysis. The absolute configurations of compounds 2 and
3 were elucidated by CD spectra. Compound 1 exhibited significantly cytotoxic activity
against CAL27 and MDAMB231 cells with IC50 values of 3.21 0.23 and 4.75 0.17 mM,
respectively, in comparison to those of positive control capecitabine (IC50: 8.20 0.75
and 5.20 0.89 mM).
Disclosure statement
No potential conflict of interest was reported by the authors.
List of abbreviations
COSY: Correlation Spectroscopy; HR-ESI-MS: high-resolution electrospray ionization mass
spectrometry; HMBC: Heteronuclear Multiple Bond Correlation; HSQC: Heteronuclear Single
Quantum Coherence; Prep-HPLC: Preparative High Performance Liquid Chromatography. CD:
Circular Dichroism Spectroscopy. CAL27: Adenosquamous carcinoma cancer cell lines;
MDAMB231: Breast cancer cell lines.
Funding
This research is funded by Vietnam National Foundation for Science and Technology
Development (NAFOSTED) under grant number 104.01-2019.18.
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